Autolevels
The Autolevels effect defines the lightest and darkest pixels in each color channel as white and black and then redistributes intermediate pixel values proportionately. As the Autolevels effect adjusts each color channel individually, it may remove or introduce colors.
In the figures below you can see the video picture before and after applying the Autolevels effect:
Before applying the Autolevels effect
After applying the Autolevels effect